(1) Field of the Invention
The present invention relates to a photonic node, photonic nodes for transmission and reception, and a method of restoring traffic upon occurrence of link failure in optical path network, which are suitable for use in a technology for accommodating an IP packet in a wavelength division multiplexing optical signal and subjecting to a cross-connection for carrying out routing.
(2) Description of Related Art
Recently, owing to a rapid deployment of the internet, the size of traffic running through the transmission network using an IP (Internet Protocol) is progressively increased. For this reason, a technology of IP over WDM (Wavelength Division Multiplexing) system using the wavelength division multiplexing scheme comes to be introduced as a technology for effectively processing the traffic which requires an exchanger having a great amount of exchanging capability.
The IP over WDM system is a system for subjecting a packet to a cross-connection operation to carry out routing. When a packet is subjected to the cross-connection operation, an information of cross-connect is utilized. When an optical signal is subjected to transmission through an optical transmitting network in which a plurality of photonic IP nodes are connected to one another, the optical signal is transmitted depending on the information of cross-connect indicating a photonic IP node as a source and a photonic IP node as a destination. Therefore, the information of cross-connect also indicates whether or not the optical signal under transmission shall be dropped at a node or transmitted through the node without being dropped. The term xe2x80x9cphotonic IP nodexe2x80x9d means an optical transmission node in the following description.
In more concretely, when an IP packet is subjected to a routing between two photonic IP nodes of the optical transmission network, initially, one of the photonic IP nodes assigns the IP packet to be routed to a particular wavelength of a wavelength division multiplexing optical signal in accordance with the IP address (destination address). Thus, the IP packet is once converted into an optical signal. Then, the wavelength division multiplexing optical signal made up with a plurality of optical signals each of which is assigned to the IP packet depending on each IP address, is transmitted through an optical transmission path and received by another photonic IP node. In this photonic IP node, only the particular IP packet is extracted from the wavelength division multiplexing optical signal. Thus, the IP packet is routed.
When the technology of IP over WDM system is introduced, even if the IP packet has a variety of addresses, or alternatively, a number of IP packets to be transmitted are created in a burst fashion, each of the photonic IP nodes can cope with the IP packets independently. Thus, the optical transmission network can deal with a great traffic which requires an exchanger to have a large exchanging capability.
Further, in order to utilize the wavelengths for optical signals more effectively, there is proposed a system in which the IP packets are accommodated into an optical signal of the same wavelength depending on the IP address or QoS (Quality of Service). According to the system, each of the photonic IP nodes carries out not only simple routing operation but operation of switching on the transmission paths of an optical signal deriving from the IP packet or operation of switching on the wavelength of the optical signal deriving from the IP packet upon carrying out routing. In this case, the terms xe2x80x9cto accommodate IP packetxe2x80x9d means xe2x80x9cto convert the IP packet into an optical signalxe2x80x9d. The terms will be utilized as the same meaning in the following description. Also, the term xe2x80x9cswitching on IP packetxe2x80x9d is sometimes referred to as xe2x80x9cIP packet switchingxe2x80x9d. In addition, in the following description, a transmission path is sometimes referred to as an optical path.
When an optical signal is received by a photonic IP node, the photonic IP node examines the destination address of the received optical signal. If the optical signal is one that is to be dropped at the photonic IP node, the photonic IP node extracts the IP packet to be dropped from the optical signal. The rest of the optical signal is returned to an optical path switching which corresponds to the layer 1 and then subjected to an IP packet switching which corresponds to the layer 2. In this manner, IP packet can undergo a routing operation with the aid of optical add/drop function.
FIG. 23 is a diagram schematically showing the optical add/drop function. A photonic IP node shown in FIG. 23 has input ports 1, 2 and output ports 3, 4. A wavelength division multiplexing optical signal composed of a plurality of optical signals having different wavelengths is supplied to the input port 1 whereas an IP packet of another node destination (destination of another photonic IP node) is supplied to the input port 2. This IP packet is subjected to a photoelectric conversion and a resultant signal is generated from the output port 3. In this case, of the plurality of optical signal which is supplied from the outside at the input port 1 and multiplexed in a wavelength division manner, an optical signal with a destination of this node is branched and dropped at the output port 4. On the other hand, of the plurality of optical signals which is multiplexed in a wavelength division manner, an optical signal with a destination of another node is passed through the output port 3 and added together with the optical signal which is supplied at the input port 2 and photoelectric converted. The optical signal resulting from the add-operation is transmitted to another node.
FIG. 24 is a physical arrangement of the photonic IP node. The photonic IP node 81 shown in FIG. 24 has input transmission paths 81a, 81b, output transmission paths 81d, 81e, an optical cross-connect apparatus 81c, an ATM exchanger 81f, routers (access router) 81g, 81h, 81i. IP packets are supplied to the node at the routers 81g, 81h, 81i, and each of the IP packets is assigned to an optical signal of a wavelength corresponding to the IP address. In this way, a plurality of optical signals are transmitted from the left side of FIG. 24 to the right side of the same. The plurality of optical signals is supplied to the node at the input transmission paths 81a, 81b. At the optical cross-connect apparatus 81c, of the plurality of optical signals which are multiplexed in a wavelength division manner, an optical signal with a destination of this node is dropped as a signal with a destination of this node. Rest of the optical signals are regarded as those with another node destination, and hence multiplexed together with the added IP packet and transmitted to other node from a desired one of the output transmission paths 81d, 81e which is selected in accordance with the wavelength.
The ATM exchanger 81f is a unit for classifying the IP packets supplied from a plurality of photonic IP nodes and bundle the same depending on the IP address. Thus, the ATM exchanger 81f can be regarded as an electric switch for switching IP packets as an electric signal. The ATM exchanger 81f is provided, at the side of the optical cross-connect apparatus 81c, with switching elements for superimposing the assigned IP packet on an optical signal of a predetermined wavelength depending on the IP address and generate the same therefrom. When the ATM exchanger 81f functions with the switching element, the unit can serve as a packet switch unit.
The optical cross-connect apparatus 81c transfers IP packets contained in the optical signal with a destination of the own node to the ATM exchanger 81f. The optical cross-connect apparatus 81c also generates an optical signal supplied from the ATM exchanger 81f to another photonic node. Further, the optical cross-connect apparatus 81c transfers an optical signal of which address is not own node, to the adjacent node. Thus, the optical cross-connect apparatus 81c serves as an optical path switch unit. Also, the optical cross-connect apparatus 81c is arranged to include a plurality of space switches.
The space switch is arranged to have a plurality of input ports and a plurality of output ports. An optical signal supplied to the space switch at the input port thereof is generated from a desired output port in accordance with an electric control signal. For example, the space switch may be arranged to have 16 input ports and 32 output ports, and 16 optical signals supplied to the input ports are generated from any of the 32 output ports.
FIG. 25 is a diagram showing an arrangement in terms of the logic of a photonic IP node, and hence the diagram shows the construction shown in FIG. 24 in more detail. As shown in FIG. 25, an optical path switch unit 82c provided in a photonic IP node 82 shown in FIG. 25 is supplied with an optical signal multiplexed in a wavelength division manner from a plurality of neighboring photonic IP nodes (not shown) through input transmission paths 83a and 83b. Each of the optical signals are branched by branching units 82a and 82b, and an optical signal having a wavelength of xcex1, an optical signal having a wavelength of xcex2, . . . , and an optical signal having a wavelength of xcexn are supplied to an optical path switch unit 82c. 
On the other hand, IP packets are supplied from routers 82g, 82h, . . . , 82i, 82j to a packet switch unit 82f. A plurality of buffers 84a provided within the packet switch unit 82f are utilized for holding the IP packet temporarily. Further, of the IP packets supplied in order, the first supplied IP packet is outputted first. The IP packets accumulated in the buffers 84a are sequentially outputted and supplied to the packet switch 84b. A plurality of wavelength division multiplexing optical signals having wavelengths of xcex1 to xcexn are prepared on the output side of the packet switch 84b. The number of the optical signals corresponds to the number of output transmission paths 82d, 82e, . . . , on the output side of the optical path switch unit 82c. 
For example, an IP packet from the router 82h is supplied through the buffer 84a to the packet switch 84b in which it is assigned with an optical path with the wavelength of xcex1. Further, an IP packet from the router 82j is supplied through the buffer 84a to the packet switch 84b in which it is also assigned with the wavelength of xcex1. Thus, the IP packets supplied from the two routers 82h and 82j are accommodated in the optical signal of the wavelength of xcex1.
In the optical path switch 82c, the optical signals supplied from the input transmission paths 82a and 82b are subjected to a cross-connect operation together with the optical signals supplied from the packet switch unit 82f. Then, multiplexing units 82d and 82e multiplex the resultant optical signals together with optical signals sent from another path. The multiplexed signals are outputted from the output transmission paths 83c and 83d. 
Of the optical signals supplied to the optical path switch unit 82c, an optical signal with the own node destination is dropped from the output port 84c and converted into an IP packet as an electric signal in the photoelectric converters (O/E converter) 82k and 82l. This IP packet is fed to the packet switch unit 82f. In this case, the reason why the IP packet with the own node destination is again fed to the packet switch unit 82f is that the signal can be relayed by another photonic IP node or the IP packet is assigned to an optical path of a different wavelength is assigned.
For this reason, the packet switch unit 82f assigns predetermined wavelengths to IP packets supplied from the routers 82g, . . . , 82j provided in the own node and an IP packet with another node destination among the IP packets dropped from the output ports. Further, the optical path switch provided within the optical path switch unit 82c carries out path switching, whereby IP packets are accommodated in an optical path of the predetermined wavelength and outputted from the output transmission paths 83c and 83d. 
FIG. 26 is a diagram showing an arrangement of the packet switch unit. The packet switch unit 85 shown in FIG. 26 is a unit for processing a great number of IP packets and assigns the IP packets to an optical signal. The packet switch unit 85 is composed of three stages of switch units 85a, 85b and 85c. The packets undergoing the switch units are switched depending on their IP address and branched in accordance with the transmission wavelength to be outputted. For example, in the switch unit 85a, IP packets of n systems (n is an integer) supplied from the left side of FIG. 26 are accumulated within buffers B11 to B1n. The IP packets generated from the buffers B11 to B1n are supplied to m (m is an integer) packet switches SW1 to SWm. The IP packets supplied to the packet switches SW1 to SWm are branched and generated therefrom. Further, a switching operation of the similar manner is also carried out in the switch units 85b and 85c, whereby the IP packets are branched from the switch unit 85c in accordance with the wavelength for transmission and outputted from the same.
Since the processed IP packets are transmitted to another photonic IP nodes by an optical signal of a predetermined wavelength, the wavelength of the optical signal functions as an indication indicative of a routing of the IP packet. Therefore, when a photonic IP node effects a routing operation on the IP packets, the photonic IP nodes utilizes the optical path instead of a path as an electric signal for the routing of the IP packets.
Accordingly, in an optical transmission network using an IP over WDM system, photonic IP nodes settle optical paths alternately. The optical transmission network will be referred to as an optical path network in the following description.
Now, description will be made with reference to FIGS. 27 and 28 on how traffic is established by a routing operation when normal status is maintained and the same is restored by a routing operation when link failure is brought about.
FIG. 27 is a diagram for explaining how an IP packet is transferred when the optical path network is maintained in the normal status. A wavelength network 90 shown in FIG. 27 includes photonic IP nodes 1 to 8 connected to one another by optical fibers. Thus, an optical signal in which a number of packets are multiplexed in a wavelength division manner can be transmitted in a bidirectional manner. In the optical path network 90, a control channel is utilized for transmitting optical path information concerning the source and destination of each of the wavelength division multiplexing optical signal, whereby each of the photonic IP nodes 1 to 8 can be supplied with the optical path information.
When the IP packets are branched by using wavelengths xcex1 and xcex2, the network show in FIG. 27 is managed at an availability of 0.5. The availability is an indication indicating a ratio of IP packet number accommodated by using these wavelengths to a maximum possible number of IP packets by using the wavelength at a certain time. For example, if the availability is set to 0.5, which fact means that if the maximum transmission bit rate allowable for the network is 10 Gbps which the actual transmission bit rate set to the network is 5 Gbps. Further, if the availability per photonic IP node is high/low, which means that the availability as viewed from tributary ports branched from the node is high/low.
Further, one of the photonic IP nodes, e.g., a photonic IP node 7 is formed of a router (denoted as IP) 7a, a packet switch unit (denoted as packet switch) 7b, an optical path switch unit (denoted as optical path switch) 7c. These components function similarly to those described above. The photonic IP nodes 1 to 6 and 8 other than the photonic IP node are similarly arranged.
With the above arrangement, routing for the IP packets carried out upon normal status becomes as follows. For example, a traffic for IP packet A, which is to be transferred from the photonic IP node 5 to the photonic IP node 1, is established whereas a traffic for IP packet B, which is to be transferred from the photonic IP node 2 to the photonic IP node 8, is established as follows.
Initially, IP packet A held in a router 5a of the photonic IP node 5 is assigned with an optical signal of a wavelength of xcex1 and transmitted as a wavelength division multiplexing optical signal through a path (path attached with reference L1). The wavelength division multiplexing optical signal containing the data of IP packet A is received by the photonic IP node 4, in which routing is carried out in terms of wavelength by an optical path switch unit of the photonic IP node 4. Then, the traffic for IP packet A passes through the adjacent photonic IP node 3. Likewise, the wavelength division multiplexing optical signal containing IP packet A goes through the photonic IP node 3 and the photonic IP node 2 by way of an optical fiber, and then received by the photonic IP node 1. In the photonic IP node 1, data of IP packet A with the own node destination is extracted from the wavelength division multiplexing optical signal.
Similarly, IP packet B held in a router of the photonic IP node 2 is assigned with an optical signal of a wavelength of xcex2 and transmitted as a wavelength division multiplexing optical signal through a path (path attached with reference L2). The wavelength division multiplexing optical signal containing data of IP packet B goes through the photonic IP node 1 and received by the photonic IP node 8. In the photonic IP node 8, data of IP packet B with the own node destination is extracted from the wavelength division multiplexing optical signal.
Conversely, if link failure is brought about in the optical path network 90, the traffic is restored as described below with reference to FIG. 28. That is, FIG. 28 is a diagram for explaining how traffics for transferring the IP packets are restored if link failure is brought about in the wavelength path network. If link failure is brought about in fibers between the photonic IP node 1 and the photonic IP node 2 as shown in FIG. 28, an optical path is settled as illustrated in the figure. In this arrangement shown in FIG. 28, each of the photonic IP nodes 1 to 8 are similarly arranged as those shown in FIG. 27. Further, the optical path network 90 is arranged so as to detect the location where the link failure is brought about, and each of the photonic IP nodes 1 to 8 can be informed of the location where the link failure is brought about through a control channel.
With the above arrangement, when the photonic IP node 5 is informed of that link failure is brought about, the photonic IP node 5 superimposes the data of IP packet A on a wavelength division multiplexing optical signal that is to be transmitted to the side of the photonic IP node 6, instead of a wavelength division multiplexing optical signal that is to be transmitted to the side of the photonic IP node 4. Thus, the wavelength division multiplexing optical signal containing the data of IP packet A is transmitted through the photonic IP nodes 6, 7, and 8 to the photonic IP node 1 in which the signal is received (a path attached with reference L3). Likewise, when the photonic IP node 2 outputs a wavelength division multiplexing optical signal containing the data of IP packet B, the photonic IP node 2 outputs the signal to the side of the photonic IP node 3, instead of the side of the photonic IP node 1. Thus, the wavelength division multiplexing optical signal containing the data of IP packet B is transmitted through the photonic IP nodes 4, 5, 6 and 7 to the photonic IP node 8 in which the signal is received (a path attached with reference L4).
In this way, even if link failure is brought about in the network, each of the photonic IP nodes 1 to 8 properly changes the direction in which the traffic for transmitting the wavelength division multiplexing optical signal extends. Thus, the IP packet can reach its destination.
However, as described with reference to FIGS. 24 to 26, when the photonic IP nodes 1 to 8 are provided in the network, each of the nodes shall be arranged to have a great number of electric switches or switch elements and a large-sized optical cross-connecting apparatus. Moreover, the packet switch unit 85 shown in FIG. 26 is arranged as a multi-stage switch circuit network formed of switch units 85a, 85b, and 85c, and each of the units includes a great number of buffers and packet switches. Therefore, if it is intended to make the packet switch unit 85 have a large capacity, the size of the hardware necessarily become large due to the buffers, with the result that complicated control mechanism is required for the apparatus.
In addition, a wavelength to be assigned to an IP packet is fixedly determined for each photonic IP node regardless of the expected availability of the node. Further, restoration of traffic against link failure is effected in the optical path switch unit. Therefore, when a new traffic is established for recovering the link failure, the changing in the branching arrangement for IP packet transmission exclusively effected in terms of optical path is left unchanged regardless of the actual availability of the node. Accordingly, a number of wavelengths that is obliged to prepare for the optical path network 90 becomes increased, with the result that the size of the hardware apparatus becomes large.
Moreover, when link failure is brought about in the network, if all of the optical paths for optical signals are changed, the optical path network 90 will suffer from a limited allowance in selecting a wavelength necessary for wavelength assignment, which fact makes the management of the system more restrictive.
The present invention is made in view of the above aspect An object of the present invention is to provide an photonic node, photonic nodes for transmission and reception, and a method for restoring a traffic upon occurrence of link failure in a wavelength network applicable to a photonic transmission network having a large IP packet capacity in which when each of the photonic IP nodes is operated at a low availability of an optical signal, an optical transmission signal having an IP packet superimposed thereon is subjected to optical path switching, and a transmission IP packet is subjected to assignment switching to an optical signal, whereby it becomes possible to reduce a number of wavelengths utilized for transmission and it becomes possible to make the size of the photonic IP node small.
According to the present invention, there is provided a photonic node including a packet switching unit for transferring a packet with a first destination address to another photonic node in accordance with the first destination address, and an optical path switching unit connected to the packet switching unit and for transferring a packet with a second destination address by establishing traffic of an optical path for a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths.
The photonic node according to the present invention further includes a space switch unit having a couple of input ports and a couple of output ports, a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths and an add-packet with another node address being supplied thereto through the couple of input ports, respectively, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through a first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through a second output port, and buffers for holding a plurality of add-packets generated as an electric signal and supplies the add-packets to the space switch unit.
The arrangement of the photonic node according to the present invention is characterized in that the optical path switching unit is composed of a part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through the first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through the second output port. Further, the arrangement of the photonic node according to the present invention is characterized in that the packet switching unit is composed of a remaining part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength and the buffers, a packet caused by an optical signal to be dropped which is generated from the optical path switching unit and a plurality of add-packets supplied through the buffer being supplied to the packet switching unit, and a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of the add-packets being supplied to the optical path switching unit as an optical signal assigned with a predetermined wavelength depending on the destination address.
According to the above arrangement, the packet switching unit can be free from multistage arrangement, with the result that the photonic node can be made small, and the photonic transmission network can be constructed with a low cost. Moreover, the packet switching unit can be made to have a lager processing capacity simply by increasing the number of buffers to be provided. Thus, the photonic node can be managed in response to the fluctuation in the size of traffic.
According to the present invention, there is provided a photonic node including a space switch unit supplied with a wavelength division multiplexing optical signal composed of optical signals assigned with a plurality of wavelengths depending on each destination address and an add-packet with another node address, and generating an optical signal with the own node address extracted from the wavelength division multiplexing optical signal and multiplexing an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address and generating the multiplexed signal therefrom, buffers for holding a plurality of add-packets generated as an electric signal and supplying the add-packets to the space switch unit, link failure detecting unit connected to an input side and output side of the space switch unit and capable of detecting link failure occurrence and generating a detection signal based on the wavelength division multiplexing optical signal, and a traffic restoration control unit connected to the link failure detecting unit and arranged to select an optical signal contained in the wavelength division multiplexing optical signal depending on the wavelength, carry out switching among optical paths, and generate the optical signal in accordance with the reception of the detection signal from the link failure detecting unit, wherein a plurality of space switches provided in the space switch unit are arranged as an optical path switching unit such that an optical signal with the own node address is extracted from the wavelength division multiplexing optical signal and generated through the first output port as an optical signal to be dropped, and an optical signal having another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet having another node address are multiplexed together and generated through the second output port, and the plurality of space switches provided in the space switch unit and the buffers are arranged as a packet switching unit such that a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of add-packets supplied through the buffer are supplied to the packet switching unit, and that a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of the add-packets are supplied to the optical path switching unit as an optical signal assigned with a predetermined wavelength depending on the destination address.
According to the present invention, there is provided a photonic node provided with a space switch unit having a first input port at which a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths is received, a second input port at which an add-packet with another node address is received, a first output port from which an optical signal extracted from the wavelength division multiplexing optical signal is generated as an optical signal to be dropped, and a second output port from which an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by the add-packet with the another node address multiplexed with that optical signal are generated. The photonic node of the present invention includes a packet switching unit supplied with a packet caused by an optical signal to be dropped which is generated from the first output port and the add-packet from the second input port, and generating a packet caused by an optical signal to be dropped and a plurality of the add-packets as an optical signal assigned with a predetermined wavelength depending on the destination address, an optical path switching unit for branching an optical signal with the own node address extracted from the wavelength division multiplexing optical signal which is supplied from the first input port and generating through the first output port as an optical signal to be dropped, and multiplexing an optical signal with another node address and an optical signal from the packet switching unit together and generating the multiplexed signal from the second output port, link failure detecting unit connected to an input side and output side of the space switch unit and capable of detecting link failure occurrence and generating a detection signal based on the wavelength division multiplexing optical signal, and a traffic restoration control unit connected to the link failure detecting unit and arranged to select an optical signal contained in the wavelength division multiplexing optical signal depending on the wavelength, carry out switching among optical paths, and generate the optical signal in accordance with the reception of the detection signal from the link failure detecting unit.
According to the present invention, the link failure detecting unit may be arranged to include an optical link break detecting unit connected to the input side of the space switch unit and arranged to generate a first switching trigger signal if the node fails to receive the wavelength division multiplexing optical signal, and a monitoring packet receiving unit connected to the output side of the space switch unit and arranged to generate a second trigger signal if the monitoring packet receiving unit fails to receive a monitoring packet which is sent at a predetermined time interval from another node as an electric signal.
Further, according to the present invention, the traffic restoration control unit may be arranged to include a path switching control unit connected to the optical link break detecting unit and the monitoring packet receiving unit, and arranged to detect link failure if a predetermined time duration has elapsed till the first trigger signal is last received from the optical link break detecting unit or the second trigger signal is last received from the monitoring packet receiving unit, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal, and a buffer reading/packet switching control unit connected to the monitoring packet receiving unit and arranged to detect link failure if a predetermined time duration has elapsed till the second switching trigger signal is last received from the monitoring packet receiving unit, change a reading order of the plurality of add-packets held in the buffers, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal.
According to the above arrangement, an operation for establishing traffic for recovering the link failure can be carried out not only by the optical path switching unit but also the packet switching unit. Therefore, the number of wavelengths to be prepared in the optical transmission network can be decreased, the availability of the optical path network is improved, and the network can be managed in a more efficient manner.
According to the present invention, the space switch unit may be arranged to include a first packet switch composed of m (m is an integer) packet switches each having an input port at which the add-packet and the packet caused by an optical signal to be dropped are supplied and an output port from which an optical signal assigned with a predetermined wavelength depending on the destination address is generated, a first space switch composed of kxe2x88x92m (k is an integer) switches each of which is arranged as an nxc3x972n (n is an integer) matrix switch having n input ports at which an optical signal having one of plurality of differing wavelengths contained in the wavelength division multiplexing optical signal is supplied, and 2n output ports from which an optical signal having the same wavelength as one of plurality of differing wavelengths, a second space switch composed of 2n switches each of which is arranged as a kxc3x97k matrix switch having k input ports at which an optical signal from the first packet switch and an optical signal from the first space switch are supplied, and k output ports from which an optical signal supplied from the k input ports is output to a path selected in a predetermined manner, a third space switch composed of kxe2x88x92m switches each of which is arranged as a 2nxc3x97n matrix switch having 2n input ports at which an optical signal from the second space switch is supplied, and n output ports from which an optical signal supplied from the 2n input ports is output in accordance with a selection depending on the wavelength, and a fourth space switch composed of m switches each of which is arranged as a 2nxc3x97n matrix switch having 2n input ports at which an optical signal from the second space switch is supplied, and n output ports from which an optical signal supplied from the 2n input ports is output in accordance with a selection depending on the wavelength.
Alternatively, the space switch unit may be arranged to include a second packet switch composed of m (m is an integer) packet switches each having k input ports at which the add-packet and the packet caused by an optical signal to be dropped are supplied and 2k output ports from which an optical signal assigned with a predetermined wavelength depending on the destination address is generated, a fifth space switch composed of n-m (n is an integer) switches each of which is arranged as a kxc3x972k matrix switch having k input ports at which the wavelength division multiplexing optical signal is supplied, and 2k output ports from which an optical signal having the same wavelength is branched and generated, an optical branching unit composed of 2k optical couplers for coupling to each other m optical signals generated from the packet switches of the second packet switch, respectively, and n-m optical signals generated from kxc3x972k matrix switch of the fifth space switch, respectively, and branching and generating an optical signal resulting from the wavelength division multiplexing caused by the photocoupling into n signals, a sixth space switch composed of n-m switches each of which is arranged as 2kxc3x97k matrix switch having 2k input ports at which the wavelength division multiplexing optical signal caused by the photocoupling generated from the optical branching unit and k output ports from which the wavelength division multiplexing optical signal caused by the photocoupling is generated under condition of wavelength division multiplexing, a seventh space switch composed of m switches each of which is arranged as 2kxc3x97k matrix switch having 2k input ports at which the wavelength division multiplexing optical signal caused by the photocoupling generated from the optical branching unit and k output ports from which the wavelength division multiplexing optical signal caused by the photocoupling is generated under condition of wavelength division multiplexing, and a wavelength selecting unit composed of nxc3x97k optical filters, supplied with optical signals from the sixth space switch and the seventh space switch, selecting an optical signal with a particular wavelength from the optical signals, and generating the selected signal.
According to the above arrangement, packets can be changed over in the space switch which can be free from the multistage construction. Therefore, the size of the switch unit can be made small and the photonic node can also be made small.
According to the present invention, there is provided a photonic node for signal transmission including a packet switching unit for transferring a packet with a first destination address to another photonic node in accordance with the first destination address, and an optical path switching unit connected to the packet switching unit and for transferring a packet with a second destination address by establishing connection to an optical path of a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths. The photonic node for signal transmission includes a space switch unit having a couple of input ports and a couple of output ports, a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths and an add-packet with another node address being supplied thereto through the couple of input ports, respectively, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through a first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through a second output port, buffers for holding a plurality of add-packets generated as an electric signal and supplies the add-packets to the space switch unit, and a monitoring packet transmitting unit for generating a packet as an electric signal at a predetermined time interval. The arrangement of the photonic node for signal transmission is characterized in that the optical path switching unit is composed of a part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through the first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through the second output port. The arrangement of the photonic node for signal transmission is also characterized in that the packet switching unit is composed of a remaining part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength and the buffers, a packet caused by an optical signal to be dropped which is generated from the optical path switching unit and a plurality of add-packets supplied through the buffer being supplied to the packet switching unit, and a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of the add-packets being supplied to the optical path switching unit as an optical signal assigned with a predetermined wavelength depending on the destination address.
According to the above arrangement, a photonic node for detecting link failure can be made small.
According to the present invention, there is provided a photonic node for signal reception including a packet switching unit for transferring a packet with a first destination address to another photonic node in accordance with the first destination address, and an optical path switching unit connected to the packet switching unit and for transferring a packet with a second destination address by establishing connection to an optical path of a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths. The photonic node for signal reception according to the present invention a space switch unit having a couple of input ports and a couple of output ports, a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths and an add-packet with another node address being supplied thereto through the couple of input ports, respectively, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through a first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through a second output port, buffers for holding a plurality of add-packets generated as an electric signal and supplies the add-packets to the space switch unit, a monitoring packet receiving unit connected to the output side of the space switch unit and arranged to generate a second trigger signal if the monitoring packet receiving unit fails to receive a monitoring packet which is sent at a predetermined time interval from another node as an electric signal, a buffer reading/packet switching control unit connected to the monitoring packet receiving unit and arranged to detect link failure if a predetermined time duration has elapsed till the second switching trigger signal is last received from the monitoring packet receiving unit, change a reading order of the plurality of add-packets held in the buffers, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal, and a path switching control unit connected to the monitoring packet receiving unit, and arranged to detect link failure if a predetermined time duration has elapsed till the second trigger signal is last received from the monitoring packet receiving unit, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal. The photonic node for signal reception according to the present invention is characterized in that the optical path switching unit is composed of a part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through the first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through the second output port, and the packet switching unit is composed of a remaining part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength and the buffers, a packet caused by an optical signal to be dropped which is generated from the optical path switching unit and a plurality of add-packets supplied through the buffer being supplied to the packet switching unit, and a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of the add-packets being supplied to the optical path switching unit as an optical signal assigned with a predetermined wavelength depending on the destination address.
According to the present invention, there is provided a photonic node for signal reception including a packet switching unit for transferring a packet with a first destination address to another photonic node in accordance with the first destination address, and an optical path switching unit connected to the packet switching unit and for transferring a packet with a second destination address by establishing connection to an optical path of a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths. The photonic node for signal reception includes a space switch unit having a couple of input ports and a couple of output ports, a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths and an add-packet with another node address being supplied thereto through the couple of input ports, respectively, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through a first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through a second output port, buffers for holding a plurality of add-packets generated as an electric signal and supplies the add-packets to the space switch unit, an optical link break detecting unit connected to the input side of the space switch unit and arranged to generate a first switching trigger signal if the node fails to receive the wavelength division multiplexing optical signal, a monitoring packet receiving unit connected to the output side of the space switch unit and arranged to generate a second trigger signal if the monitoring packet receiving unit fails to receive a monitoring packet which is sent at a predetermined time interval from another node as an electric signal, a path switching control unit connected to the optical link break detecting unit and the monitoring packet receiving unit, and arranged to detect link failure if a predetermined time duration has elapsed till the first trigger signal is last received from the optical link break detecting unit or the second trigger signal is last received from the monitoring packet receiving unit, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal, and a buffer reading/packet switching control unit connected to the monitoring packet receiving unit and arranged to detect link failure if a predetermined time duration has elapsed till the second switching trigger signal is last received from the monitoring packet receiving unit, change a reading order of the plurality of add-packets held in the buffers, and select an optical signal of the space switch unit for controlling switching of the destination of the optical signal. The photonic node for signal reception according to the present invention is characterized in that the optical path switching unit is composed of a part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength, an optical signal with the own node address being extracted from the wavelength division multiplexing optical signal and generated through the first output port as an optical signal to be dropped, and an optical signal with another node address contained in the wavelength division multiplexing optical signal and an optical signal caused by an add-packet with another node address being multiplexed together and generated through the second output port, and the packet switching unit is composed of a remaining part of the space switch unit for branching each optical signal of the wavelength division multiplexing optical signal depending on its wavelength and the buffers, a packet caused by an optical signal to be dropped which is generated from the optical path switching unit and a plurality of add-packets supplied through the buffer being supplied to the packet switching unit, and a packet caused by an optical signal to be dropped which is generated from the optical path switching unit through the first output port and a plurality of the add-packets being supplied to the optical path switching unit as an optical signal assigned with a predetermined wavelength depending on the destination address.
According to one variation of the present invention, the buffer reading/packet switching control unit may be arranged to respond to the time duration even if the time duration is variable, and the path switching control unit is also arranged to be capable of responding to the time duration even if the time duration is variable.
According to the above arrangement, the photonic node for detecting link failure can also be made small.
According to the present invention, there is provided a photonic node including an optical path switching unit supplied with optical signals having a plurality of wavelengths different from one another at a plurality of input ports, subjecting the optical signals having a plurality of wavelengths different from one another to a switching operation effected by an opto-space switch of a multi-stage arrangement, and a buffer connected to a predetermined number of ports of the plurality of input ports provided in the optical path switching unit, holding a packet with a destination address and supplying the packet to the optical path switching unit at the predetermined number of ports, wherein a part of the opto-space switch of the optical path switching unit is replaced with a packet switching unit for converting the packet supplied to the buffer into an optical signal assigned with a predetermined wavelength depending on the destination address and generating the optical signal.
Accordingly, if the photonic node is arranged as above, it becomes possible to manage the photonic node in response to the fluctuation of the size of traffic fed to the photonic node, with the result that extendability of the system can be improved in response to the increase of number of necessary wavelengths.
According to the present invention, there is proposed a method of restoring traffic upon occurrence of link failure in an optical path network which is composed of a plurality of photonic nodes connected to one another, a photonic node including a packet switching unit for transferring a packet with a first destination address to another photonic node in accordance with the first destination address, and an optical path switching unit connected to the packet switching unit and for transferring a packet with a second destination address by establishing connection to an optical path of a wavelength division multiplexing optical signal composed of optical signals of a plurality of wavelengths. The method includes the steps of processing an input packet by receiving a wavelength division multiplexing optical signal composed of optical signals assigned with a plurality of wavelength depending on the first destination address, and extracting an optical signal with the own node address and an optical signal with another node address from the wavelength division multiplexing optical signal and generating the extracted signals, processing an output packet by decoding a packet from the optical signal generated at the step of processing an input packet, allocating the decoded packet and a plurality of add-packets generated as electric signals to an optical signal with a predetermined wavelength depending on the destination address, and generating the optical signals, extracting a number of nodes which are designated by destination addresses of the optical signals assigned with the packets at the step of processing an output packet, allocating a predetermined wavelength to the optical signal generated at the step of processing the input packet and the optical signal generated at the step of processing the output packet so as to secure the corresponding wavelength, and then generating the optical signal assigned with the predetermined wavelength, detecting an occurrence of link failure based on the wavelength division multiplexing optical signal and generating a detection signal, and establishing traffic avoiding the link failure by operating at least one of the packet switching unit and the optical path switching unit so that the packet can be transmitted through the established traffic to the photonic node corresponding to the destination address, based on the number of destination nodes determined at the step of extracting the number of destination nodes.
In the above-proposed method of restoring traffic according to the present invention, the step of detecting an occurrence of link failure may be arranged as an optical link break detecting step in which if the wavelength division multiplexing optical signal is absent in being received by the node for a predetermined period of time, then it is determined that any link failure is brought about. The step of detecting an occurrence of link failure may be arranged as a monitoring packet receiving step in which a monitoring packet transmitted at a predetermined interval is received and if the monitoring packet is absent in being received for a predetermined period of time, then it is determined that any link failure is brought about. Further, the step of detecting an occurrence of link failure may be arranged to include a first extending step for extending the period of time concerning the detection of the absence in receiving the monitoring packet in the monitoring packet receiving step, and a first detecting step in which if the wavelength division multiplexing optical signal is absent in being received by the node for a predetermined period of time, then it is determined that any link failure is brought about.
Furthermore, the step of detecting an occurrence of link failure may be arranged to include a second extending step for extending the period of time concerning the detection of the absence in receiving the wavelength division multiplexing optical signal in the optical link break detecting step, and a second detecting step in which if the monitoring packet is absent in being received for the predetermined period of time, then it is determined that any link failure is brought about.
In the above-proposed method of restoring traffic according to the present invention, the step of establishing traffic avoiding the link failure may be arranged such that if it is determined that the number of nodes of destination address is singular in the node number extracting step, only the optical path of the optical signal generated at the optical path processing step is changed, whereas if it is determined that the number of node of destination address is plural in the node number extracting step, the optical path of the optical signal generated at the optical path processing step is changed, and also the decoded packet and the add-packet are assigned with a wavelength corresponding to the destination address. Further, the step of establishing traffic avoiding the link failure may be arranged such that the traffic is rerouted at the source node and the destination node in such a manner that the optical signal is assigned with a substituting path which permits the optical signal to be transferred to the destination node. Furthermore, the step of establishing traffic avoiding the link failure may be arranged such that the restoration of traffic is handled by the nodes neighboring the failed link in such a manner that the optical signal is assigned with a substituting path which permits the optical signal to be transferred to the destination node.
In addition, in the above-proposed method of restoring traffic according to the present invention, the step of establishing traffic avoiding the link failure may be arranged such that an identical wavelength is assigned to an optical signal to be transmitted through a section to which the optical path is settled. Further, the step of establishing traffic avoiding the link failure may be arranged such that differing wavelengths are assigned to optical signals to be transmitted through a section to which the optical path is settled.
Furthermore, according to the present invention, there is proposed a method of restoring traffic avoiding link failure in an optical path network in which a plurality of packets each having a destination address are converted into optical signals of a predetermined wavelength and transferred depending on the destination address. The method includes the steps of extracting the number of nodes of the destination address of the optical signals which are converted from the plurality of packets, converting the plurality of packets into optical signals having an identical wavelength if the number of nodes is determined to be plural at the node number extracting step, and converting the packet into an optical signal having a wavelength depending on the destination address if the number of nodes is determined to be singular at the node number extracting step.
According to the above-described arrangement, packet switching can be carried out as well as wavelength switching is. Therefore, traffic restoration is effectively carried out, with the result that extendability of the system can be improved in response to the increase of number of necessary wavelengths.